Safety belt

ABSTRACT

A safety belt for tightly holding an occupant of a seat for vehicles such as an automobile, said safety belt being equipped with a shock absorbing means having a rigid plastics foam body, a receptacle with a uniform cross-section and a bottom plate, and a pusher having a tapering face the projected area of which is less than 70 percent of the cross-sectional area of said plastics foam body, said foam body being held in said receptacle between the pusher and the bottom plate, said pusher being movable toward said bottom plate when a tension is generated by the movement of an occupant supported by the belt so that said plastics foam body is deformed and displaced by the passage of said pusher and the kinetic energy developed by the movement of the occupant is absorbed.

United States Patent [191 Komatsu et a].

[ Feb.5,1974

[ SAFETY BELT [75] Inventors: Noboru Komatsu; Choji Nozaki;

Toshio Kurauchi; Toshihiko Sakai, all of Nagoya, Japan [63]Continuation-impart of Ser. No. 97,989, Dec. 14,

1970, abandoned.

[52] US. Cl 297/386, 297/389, 188/1 C [51] Int. Cl A62b 35/60 [58] Fieldof Search 297/386; 188/1 C; 260/922 [56] References Cited UNITED STATESPATENTS 3,198,288 8/1965 Presunka 297/386 X 3,680,913 3/1972 Seybold297/386 3,532,380 10/1970 Studer et al. 297/386 3,232,383 2/1966 Moberg297/386 3,561,819 2/1971 Renneker. 297/386 3,380,557 4/1968 Peterson188/1 C 2,724,463 11/1955 Becker 297/386 X 3,398,812 8/1968 Peterson297/386 X FOREIGN PATENTS OR APPLICATIONS 965,836 9/1962 Great Britain188/1 C OTHER PUBLICATIONS Properties of Rigid and Semi-Rigid UrethaneFoams; Aug. 1957.

E. Tufts Handbook of Foamed Plastics; Lake Publishing Corp.; 1965.

Primary Examiner-James T. McCall Attorney, Agent, or Firm-Blum,Moscovitz, Friedman & Kaplan 5 7 ABSTRACT A safety belt for tightlyholding an occupant of a seat for vehicles such as an automobile, saidsafety belt being equipped with a shock absorbing means having a rigidplastics foam body, a receptacle with a uniform cross-section and abottom plate, and a pusher having a tapering face the projected area ofwhich is less than 70 percent of the cross-sectional area of saidplastics foam body, said foam body being held in said receptacle betweenthe pusher and the bottom plate, said pusher being movable toward saidbottom plate when a tension is generated by the movement of an occupantsupported by the belt so that said plastics foam body is deformed anddisplaced by the passage of said pusher and the kinetic energy developedby the movement of the occupant is absorbed.

c a m anraw ns ti w s PATENTEUFEB SIM 3.79020 SHEEIIUF'I N I I I J I Q I3 I I I I E A P B I: II I I I I I II I I I I la 0 F R62 N'GbV-JfiDISPLACEMENT F/G.2 F/G.3

DISPLACEMENT DISPLACEMENT PAIENTEUFEB 5'974 5 (7V0? Nolssaadwoa 10 20DISPLACEMENT (mm) 20 5'0 DISPLACEMENT (mm) PATENTED 5 SHEET 5 BF 7 FIG/OE 0&9 363%:8

D/SPLACEMENT (mm) CROSS-REFERENCE TO RELATED APPLICATION Thisapplication is a Continuation-In-Part of my copending application Ser.No. 97,989 filed Dec. 14, 1970 now abandoned.

BACKGROUND OF THE INVENTION Although safety belts are in wide use andtheir use is being expanded both with respect to the installation ofbelts and with respect to the introduction of shoulder harnesses,nevertheless, the protection afforded by such belts is not nearly sogreat as is desired. The difficulty is that although such belts mayrestrain the wearer sufficiently to avoid the so-called second collisionthey do not provide for absorption of the kinetic energy of the wearer.As a result, the wearer can be severely injured by the force exerted bythe belts themselves. One attempt to meet with this difficulty is thebag expanded by explosion. The protection provided by such a device isstill in question. It is obvious that a satisfactory means of absorbingthe kinetic energy of a vehicle passenger when the vehicle is subjectedto sudden acceleration or deceleration is still needed.

SUMMARY OF THE INVENTION In a safety belt assembly for holding apassenger safely in a moving vehicle, a receptacle contains a rigidcellular foam between a pusher and a bottom plate. The receptacle andthe pusher are so related to the safety belt and to the vehicle thatrapid deceleration or acceleration of the vehicle as by a collisioncauses the pusher to be drawn through the rigid foam displacing the foamtoward the wall of the receptacle and destroying the foam. The kineticenergy of the passenger is absorbed in the process. The projected areaof the pusher transverse to the receptacle should be about 70 percent ofthe transverse cross-sectional area of the rigid foam.

Accordingly, an object of the present invention is to provide a safetybelt to absorb the kinetic energy developed by the movement of anoccupant of a vehicle to moderate the shock and to decrease the forceacting on the occupant when the vehicle is involved in a rapidacceleration or deceleration as in a collision.

Another object of the present invention is to provide a safety belt toabsorb as much of the kinetic energy as possible within the range ofdisplacement allowable by virtue of the design of the vehicle.

A further object of the present invention is to provide a safety beltcomprising means to absorb the kinetic energy by the displacement anddestruction of a plastics foam body.

A still further object of the present invention is to provide a safetybelt comprising means to absorb the kinetic energy by destroying aplastics foam body by a pusher having a tapering pushing face.

Still other objects and advantages of the invention will in part beobvious and will in part be apparent from the specification.

The invention accordingly comprises the features of construction,combination of elements, and arrangement of parts which will beexemplified in the construction hereinafter set forth, and the scope ofthe invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of theinvention, reference is had to the following description taken inconnection with the accompanying drawings, in which:

FIG. I is the ideal load-displacement curve of a safety belt;

FIGS. 2 and 3 are the load-displacement curves respectively of a belt ofnylon filament and of polyester filament;

FIGS. 4 to 10 are the diagrammatic displacement curves of variousplastics foams;

FIG. 11 is a view in partial section of a safety belt in accordance withthe present invention as mounted in a vehicle and worn by a passenger;

FIG. 12 is a cross-sectional view of a shock-absorbing device inaccordance with the present invention;

FIG. 13 shows schematically relative dimensions of a portion of ashock-absorbing means;

FIGS. 14 and 15 are cross-sectional views of a shock absorbing meansmodified partially from the shock absorbing means of FIG. 12;

FIG. 16 is a partially broken away perspective view of theshock-absorbing means of a second embodiment of the present invention;

FIGS. 17 and 18 are partial perspective views of the modified T-shapedmembers of the shock absorbing means of FIG. 16; and

FIG. 19 is a partially broken away perspective view of theshock-absorbing means of a third embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to prevent occupantsof seats from injuries due to shock in accidents of aircraft, ships orautomobiles, or like vehicles hereinafter called vehicles, safety beltsto hold the occupants to seats are employed. It is necessary that safetybelts should be strong enough to sustain a severe impact load due toabrupt deceleration of the mass of the occupant and at the same time thesafety belt should moderate the shock by absorbing the kinetic energydeveloped by the motion of the occupant. In the process, a slightelongation of the belt is permissible. When the elongation. of the beltis too large, however, the occupant of a seat will be exposed to asecondary collision such as with an instrument board or other part ofthe vehicle, mechanical or otherwise, due to the displacement ormovement of the occupant relative to the seat.

Therefore, the safety belt should satisfy both (1) the function oflimiting the movement of the occupant and thereby preventing thesecondary collision when the occupant or the vehicle occupied by him issubjected to a shock, and (2) the function of absorbing the kineticenergy developed by the occupant or the vehicle in order to moderate theshock and decrease the force acting against the occupant.

In order to accomplish both functions as mentioned above, the safetybelt should be such that the load (force applied to the occupant) riseswithin a small displacement range at the beginning of the shock, andwhen the load reaches a certain value within the range insufficient todamage a human body, the displacement may increase without increasingthe load acting on the belt, thereby absorbing a large amount of kineticenergy resulting from the force acting on the occupant;

loadalso, the final displacement of the occupant is maintained within apredetermined value.

FIG. 1 shows an ideal displacement-load character curve for a safetybelt as mentioned hereinabove, wherein the elongation of the safety beltis shown as the abscissa and the load applied on the safety belt isshown as the ordinate. At the beginning of a shock, the curve ofdisplacement-load rises sharply as shown by A with a small displacementOF until the load reaches a predetermined value OE within the rangeinsufficient to damage a human body, and then levels off at a plateaudisplacement as shown by AB without change in the load of OE until thedisplacement reaches a predetermined value OG. (The load OE at thisplateau portion will be termed the plateau load hereinafter). It isnecessary that the elongation of the safety belt should be limited to avalue previously determined in designing of a vehicle to prevent asecondary collision. When such displacement is set to be OH, the load isincreased by increasing the displacement of the belt within thedisplacement GH as shown by the loaddisplacement curve BC, taking theload OJ at the displacement OH as the maximum load to which the occupantmay be safely subjected. The point K in the drawing shows the breakingpoint of the safety belt. The load at the breaking is shown by CL andthe displacement at the breaking is shown by OM.

When the load, due to the shock, is reduced at the point C to zero, thedisplacement OD due to plastic deformation is retained in the safetybelt. The fact that the'final displacement OD is small in comparison tothe maximum displacement OH at the point of C means that the belt has ahigh elastic recovery or a high spring action. This is not desirablesince it holds the occupant too tightly and rigidly due to contractioncaused by the elasticity when the shock is terminated. Accordingly, thedisplacement OD should preferably be as great as possible in ratio tothe displacement OH, and the displacement of the former, due to plasticdeformation, should preferablybe near to or greater than 60 percent inpercentage to the latter. (The ratio expressed in percent of the finaldisplacement to the maximum displacement will be called thefinaldisplacement ratio or permanent set hereinafter.) The load OE at thepoints A and B should be, of course, within the range insufficient todamage a human body and it should be safely designed by setting thevalue of the load OJ at the point of C being markedly smaller than theload OL at the breaking point K of the belt.

When the load applied on the belt due to shock is less than the load OE,the displacement-load curve rises along the line OA, and when the shockis ended, it returns along the line OA so that there is little permanentplastic deformation, whereas when the shock is greater, the curve ofdisplacement'load proceeds along the line AB, wherein the load is notincreased beyond OE and only the displacement is increased. If the shockand displacement should end at the point P, the maximum displacementwould be OO and the maximum amount of kinetic energy absorbed by asafety belt would be equivalent to the area of the quadrilateral OAPQ.Thereafter, when the shock is ended, the part of the kinetic energyabsorbed by the belt is discharged and the final displacement becomesOR. Similarly, if the shock should end at the point C, the maximumabsorbed energy would be equivalent to the area surrounded by the linesOA, AB, BC, CD and OD. It is preferable that the safety belt shouldabsorb as much kinetic energy as possible within the range ofdisplacement allowable in vehicles as designed. For this purpose, asafety belt is ideal when it has the properties of a long plateaudisplacement at plateau load within said displacement range, and a highplateau load within the range insufficient to damage a human body(occupant) and with permanent set of about 60 percent or above, as shownby the curve of displacement-load in FIG. 1. Although the plateau loadfrom the point A to point B has been shown to be constant in FIG. 1, itis, of course, sufficient if it is approximately flat.

Textile belts of nylon filament or polyester filament have been employedas safety belts. The displacements caused by stretching the textilebelts and the load applied on the belt have been measured. FIG. 2 showsa load-displacement curve of a nylon belt and FIG. 3 shows that of apolyester belt. As the Figures show the load increases approximately inproportion to the increase of the displacement and no plateau load suchas the line A of FIG. 1 is observed. Accordingly, the amount of kineticenergy absorbed is small in comparison to the maximum displacement andthe permanent set is also small. Various attempts such as blending nylonfilament or polyester filament with other filaments and changing textilestructures have been made, but it is very difficult to increase theabsorbed kinetic energy and the permanent set due to the various defectssuch as decrease in the breaking load with increase in rigidity andincrease in elasticity with an increase in displacement.

The inventors have endeavored to afford safety belt functions (I) and(2) hereinbefore mentioned, not by improving the materials themselves,but by providing a novel mechanism with functions to provide the desireddisplacement and the shock abosrption, in combined form as a function ofthe belt structure.

A simple and inexpensive mechanism has been devised for providingdisplacement and shock absorption by means of plastic deformation due tothe impact load caused by the force developed by kinetic energy.

A shock absorber utilizing the viscosity resistance of oil has beenbroadly known, and while it may be possible to design a shock absorberthat repeatedly yields a load-displacement characteristic as shown inFIG. 1, such a type of mechanical shock-absorber would tend to be tooexpensive and heavy. Moreover, repeated use is not always required ofashock-absorber, since a vehicle is rarely operable immediately afterreceiving such a degree of shock that a safety belt which absorbs largeamounts of kinetic energy is actually effectuated.

From the point of view mentioned above, the inventors have disclosed inthe present invention an inexpensive material and mechanism having acharacteristic curve similar to the ideal feature shown in FIG. 1 andsufficiently inexpensive to permit abandonment after one use. Frominvestigations of the characters of displacement-load curves of variousmaterials, the fact that a plastics foam has the load-displacementcharacteristic shown by FIG. 1 and that the values of the plateau loadand the plateau load displacement depend on density of the plastic foam,provides a basis for this development.

The present invention has been established by utilizing the abovecharacteristic of plastics foams, in which a plastics foam body isjoined to a belt so as to be compressed when tension is applied to thebelt by motion of the wearer. The safety belt according to the presentinvention relieves shock by absorbing the kinetic energy of the occupantand acts to minimize and prevent the causing of injury.

The values of the plateau load and the displacement of a plastics foamto be employed in a particular application are determined by the weightof the occupant, the velocity of the vehicle in which the safety belt isto be used, the impact resistance of the occupant and the range ofmotion allowable to the occupant for eliminating the probability ofcausing a secondary collision. A safety belt containing a foam havingthe density suitable to the above conditions and large permanent setshould be selected. The plateau load of a plastics foam is, of course,affected by the area on which the load (force) acts and the length orheight in the direction of compression and there naturally arelimitations in consideration of the adaptability and purpose for usethereof. Therefore, the plastics foam, within the above limitations asto size and having a large plateau load within the range not to injurethe occupant, should be of such density as to afford a large plateaudisplacement within the predetermined displacement range, and a largepermanent set of the foam should be provided.

EXPERIMENT I A specimen of a cylindrical shape of 40mm diameter and 50mmheight prepared from a rigid polyurethane foam whose density was0.1lg/cm was subjected to compression testing by placing the specimenwith its axis in the vertical direction on an lnstron type universaltesting machine (ASTM D76-67, CONSTANT RATE-OF-SPEClMEN-EXTENSION TYPECRE), setting the bottom face closely on the machine and the top faceclosely on the pressing plate of the crosshead, and pressing down saidplate at a velocity of 50mm/min. (the same being hereinafter called asthe compression velocity) to compress said specimen in the axialdirection. The curve of compression loaddisplacement obtained bymeasuring the load acting on the pressing plate (the same beinghereinafter called the compression load) and the displacement in theaxial direction of the specimen are shown in FIG. 4.

As clearly seen from the drawing, the relationship between thedisplacement caused by the compression of the specimen and thecompression load causing said displacement is such that the loadincreases approximately linearly until about 3mm of displacement, afterwhich the curve becomes approximately constant at about 140 kg, andsubsequently shows a rapid rise at the position of the displacement overmm, finally showing a permanent set of 88 percent by recovery to a finaldisplacement of about 38 mm after the removal of the load when thecompression load is about 500 kg at the maximum displacement of about 44mm, such values being similar to the characteristics as shown in FIG. 1.It will be understood from the above that the requirements for the shockabsorbing material of the safety belt are satisfied.

EXPERIMENT 2 A rigid polyurethane foam of mm dia., 50 mm height and 0.15g/cm density was employed and subjected to compression testing as above.The test results are shown in FIG. 5. The plateau load was about 300 kg,the plateau load displacement was about 30mm and the permanent set wasabout percent. The plateau load was larger than that of Experiment .1,due to the higher density of the foam employed. This latter materialshows the property similar to FIG. 1 and is suitable for a shockabsorbing material of a safety belt.

EXPERIMENT 3 A rigid polyurethane foam of 30 mm dia., 18 mm height and0.11 g/cm density was subjected to compression testing as inExperiment 1. The test results are shown in FIG. 6 and show the propertysimilar to FIG. 1.

However, the plateau load was about 70 kg and the plateau loaddisplacement was about 10 mm, which were smaller than those ofExperiment 1 in spite of the same density. This is due to'thedifferences in the area where the compression load was applied and theheight. Therefore, it follows that the plateau load may be increased byincreasing the foam area and the amount of displacement can be increasedby increasing the foam length. The permanent set was of the preferredvalue, being about 71 percent.

EXPERIMENT 4 A rigid polyurethane foam of 20 mm dia., 16 mm height and0.32 g/cm density was subjected to compression testing as inExperiment 1. The result was about 190 kg for the plateau load, about 5mm for the plateau load displacement and about 71 percent for thepermanent set as shown in FIG. 7. The particular difference, as comparedwith the result of Experiment 1, involves an increase of the plateauload and decrease of the plateau load displacement, this being due tothe increase of density of the foam, it being understood that theplateau load increases as the density increases, while the plateau loaddisplacement decreases as th density increases. 1

, EXPERIMENT .s

A polystyrene foam of 25 mm dia., 30 mm height and 0.08 g/cm density wasemployed and subjected to ocmpression testing as in Experiment 1. Thetest result is as shown in FIG. 8. The plateau load was 45 to 100 kg andthe displacement was about 20 mm, and the displacement was conductednearly in the condition of the plateau load. Thus, the property similarto FIG. 1 in general can be observed.

EXPERIMENT 6 A polystyrene foam of 40 mm dia., 13 mm height and 0.029g/cm density was employed and subjected to compression testing as inExperiment 1. The result is shown in FIG. 9. The plateau load was about55 kg, the plateau load displacement was about 10 mm and the permanentset was about percent, and the property was similar to FIG. 11.

. EXPERIMENT 7 A soft polyurethane foam of 40 mm dia., 20 mm height and0.19 g/cm density was subjected to compression testing as inExperiment 1. The test results were as shown in FIG. 10. The permanentset and the plateau load were very small: 20 percent and 5 kg,respectively. Accordingly, the amount of the absorbed kinetic energy wasextremely small. A plastics foam with such a small permanent set wasfound to be unsuitable for shock absorbing material of the safety belt.

Although the plateau load and the plateau load displacement depend onthe area on which the load acts and the height of the plastics foam, thedimensions of the plastics foam are limited in view of the manner of usesuch as being assembled in a safety belt. A foam having 0.02 to 0.50g/cm density is suitable for practical use in a safety belt from theveiwpoint of comparatively high plateau load and plateau loaddisplacement within the limited dimensions showing the property similarto that of FIG. 1. Further, a plastics foam having a large permanent setis effective to absorb a large amount of kinetic energy, and in practicethe pennanent set should be preferably more than 60 percent.

As described above, the kinetic energy is effectively absorbed and theshock can be moderated by assembling a plastics foam whose density is0.02 to 0.50 g/cm and whose permanent set is above 60 percent into asafety belt so as to be compressed when an impact load acts onto a bodyto be protected by the belt; the intended role as a safety belt canthereby be effectively accomplished.

Details of the safety belt according to the present invention will beclearer from the description hereinafter referring to illustrativeexamples.

In applying the above-mentioned plastics foam to a seat belt, a shockabsorbing device A comprising said plastics foam is provided between oneend of a shoulder belt 21 (FIG. 11), the other end of which is connectedto lap belts 22, 23 made of a suitable material such as nylon and ananchor portion 1 of a vehicle (said device being called a shockabsorbing means hereinafter). Said shock absorbing device A contains aplastics foam 4 having an aperture 41 in the axial direction within acylindrical body 3 with bottom and with one end open, and satisfying therequirementsas mentioned above. A T-shaped member 5 for displacing thefoam consists of a pusher 51 having a tapering pushing face 511 which inthis embodiment is concave, and a connecting rod 52, one end of which isfixed axially to the central portion of the pusher 51. Said pushing face511 abuts one end face of said plastics foam 4, and the connecting rod52 penetrates through aperture 41 of the plastics foam 4 and an aperture32 at the center portion of bottom plate 31 of the cylindrical body 3. Aconnecting means 53 formed at the end of the connecting rod 52 outsidethe cylindrical body 3 is turnably connected with one end of theshoulder belt 21. On assembling, for example, one end of the connectingrod 52 is inserted into the apertures 32 and 41 of the bottom plate 31and the plastics foam 4, respectively, and said rod is screwed into saidpushing plate 51. Also, a cap 35 is placed over the open end of saidcylindrical body 3 and one end of the connecting plate 16 is turnablyconnected to a connecting means 351 provided on the center of said cap35, the other end of said plate 16 being connected to anchor portion 1of the vehicle by means of bolt 15. Where the shock absorbing device Ais thus arranged, when a tension is caused on belt 21 due to a leaningof a human body in a vehicle caused by a shock from the rear, forexample, the T-shaped member 5 acts in the direction shown by an arrow(FIG. 12) and the plastics foam 4 in a cylinder is compressed betweenthe inner surfaces of side wall 33 and of the bottom plate 31 of thecylindrical body 3 and the pushing face 511 of the pusher 51. The partof the foam 4 broken by the edge portion of the pushing face 511 isdischarged toward the side wall 33 of the cylindrical body 3 as thepusher 51 is advanced downward; energyabsorption continues until thepusher 51 contacts the bottom plate 31 of the cylindrical body 3.Therefore, a long plateau load displacement is attained with permanentset of the plastics foam. Also, the maximum absorbed energy is attaineddue to the long plateau load displacement. However, in order to attainthe long plateau load displacement mentioned above, the pusher 51 shouldbe provided with certain features which will be explained with referenceto FIG. 13. One of the features of the pusher 51 is its projectionratio, namely the ratio of the height to the base of the pusher 51.Here, we use point Y as the highest point of the tapering pushing face511, point Z as the lowest point of the pushing face 511 and point X asthe intersectional point of the line which includes the point Y and isparallel to the connecting rod 52 and the line including the point Zwhich is perpendicular to the connecting rod 52. The projection ratio isdefined as XY/XZ, and the ratio must be between 0.25 and 1.75. Iftheratio is smaller than 0.25, the plastics foam destroyed with the pushingface will not be discharged toward the side wall 33 of the cylindricalbody 3 and will be compressed between pushing face 511 and bottom 31.Therefore, the plateau load displacement will become shorter. If theratio is larger than 1.75, the distance between the tip of the pusherand the bottom plate 31 becomes too short to attain the long plateauload displacement in a given length of the shock absorbing device A.Another significant feature of the pusher 51 is the large size of thepushing area relative to the inner cross-sectional area of thecylindrical body 3. Here, we define Sp as the projected area of thepushing face 511 on a plane perpendicular to the connecting rod 52. Thepushing area Sp does not include the cross-sectional area Sc of theconnecting rod 52. Sr is the cross-sectional area of the plastics foam 4(which is also defined by the area excluding Sc from the innercross-sectional area of the cylindrical body 3). The pushing area Spmust be smaller than percent of the cross-sectional area Sr of theplastics foam. If the pushing area Sp is larger than 70 percent of thearea Sr, a part of the broken plastics foam mentioned above will clogbetween the edge of said pusher 51 and the side wall 33 of thecylindrical body 3 and will cause an abrupt stopping or irregularmovement of the pusher 51 on the way to the bottom plate 31, and theoccupant wearing the safety belt will be injured.

FIG. 14 shows a shock absorbing means comprising a cylindrical body 3with an inner diameter of 22mm, a bottom plate 31, a pusher 51 with aconical pushing face 512 having a bottom diameter of 12.5 mm and aprojection ratio of l (=XY/XZ in FIG. 13), a connecting rod 52 with adiameter of 6mm and a plastics foam 4 with an outer diameter of 22mm andwith an inner diameter of 6mm. Thus, the elements comprise a shockabsorbing means meeting the conditions presented above. The distancebetween the tip of the cone-shaped pushing face 512 and the bottom plateis approximately mm.

Next, the shock-absorbing means was tested by pulling it to measure itsplateau load, plateau load displace-.

ment and absorbed energy. Also, plastics foams with densities between0.1 to 0.5g/cm were tested. The results of the tests are shown in thefollowing chart.

Test No. l 2 3 4 5 Density of Foam (g/cm) 0.26 0.30 0.40 0.45 0.50Plateau Load (kg) 90 120 220 300 470 Plateau load displacement (mm) 9596 97 98 98 Absorbed energy (kg.rn) 8.5 II 2l 28 45 As seen from thechart, the plateau load displacement does not change much with variationin density of the plastics foam 4 and is almost the same as the distance, 100mm. between the tip of the comically-shaped pushing face 512and the bottom plate 31. However, the plateau load and absorbed energyare increased with increase in density of the plastics foam 4.

The device as shown in FIG. 15 is so constructed that the pushing face513 of the pusher S1 of a T-shaped member 51 is spherically shaped and aplastics foam 4 is integrally formed within a cylindrical body 3. Priorto forming, a T-shaped member 5 provided with a pusher 51, having apushing face 513 of a hemspherical shape, is coated with a parting agentover its surface and placed within the cylinder 3. A liquid materialfrom which a plastics foam can be formed is poured from a port (notshown) provided at a lower portion of the cylinder wall to fill thecylinder and then the liquid is treated to become foamed. Excessplastics material produced during the foaming stage is dischargedthrough a port (not shown) provided at the upper portion of thecylindrical body. Thus, a shock absorbing device (means) wherein thecylinder body is filled with plastics foam and a T-shaped member 51 isimbedded within foam 4 is formed as shown in FIG. 15. Means forconnecting said shock absorbing means with the an chor portion on thebelt end may be similar to the previously described embodiment. As theplastics foam is integrally fonned in the cylindrical body, there is nofear that the surrounding face of the foam may be damaged by the contactwith the cylindrical body due to constantly applied vibrations.

FIG.'16 shows another shock absorbing means B which comprises abox-shaped body 6 with a rectangular cross-sectional area, a T-shapedmember 7 with the samethickness as that of body 6 and two pieces ofplastics foam 8 which are held in the body 6 and on both sides ofT-shaped member 7. The box-shaped body 6 consists of a base 61 with agroove 641 and a lid 62.

i The T-shaped member 7 consists of pusher 71' with two inclined planarside'faces 711 and a connecting rod 72 having a rectangularcross-section. The pusher 71 and connecting rod 72 may be formedintegrally, or may be combined by welding. On assembling, the T-shapedmember 7 and two pieces of the plastics foam 8 are put in the base 61 asshown in FIG. 16. Then, lid 62 is put on the base 61 and riveted orbolted thereto. In this embodiment, the inclination of the pushing faces711 and the ratio of the pushing area to the compressed area are alsoimportant to attain a smooth and long plateau load displacement withoutabrupt stopping or irregular movement. The conditions of this embodimentare the same as the conditions explained with FIG. 13. When the T-shapedmember 7 connected to a belt is pulled, the inclined planar facescompress and destroy the plastics foams 8 and displace a part of thedestroyed plastics foams from both edges of the pushing faces 711. OtherT-shaped members having a constant thickness of the shock absorbingmeans B can be also employed For example, a T-shaped member having atapering pusher 73 with concave pushing faces 731 (see FIG. 17) orhaving a tapering pusher 74 with convex pushing faces 741 (see FIG. 18),may be employed and will be able to absorb the kinetic energy with arelatively long plateau load displacement.

FIG. 19 shows further shock absorbing means C connected to an anchorportion 1 of a vehicle such as a wall of the vehicle. Thisshock-absorbing means C comprises a box-shaped body 9 with a squareinner crosssection, a T-shaped member 10 having a pusher 110 withpushing faces 111 comprising a frustum of a pyramid and a connecting rod120, and a box-shaped plastics foam 11 with an aperture therethroughhaving the same cross-section as that of rod 120. The inclination of thepushing faces 111 and the ratio of the projected area of the pusher 110to the compression area are chosen to meet the specification givenabove.

In the above illustrative embodiments, shockabsorbing means in whichplastics foam is provided within a receptacle having a uniformcross-sectional area and between a pushing face of a T-shaped member anda bottom plate of the receptacle, are explained in detail. However, itis not always necessary to employ a T-shaped member with the pusher forcompressing the plastics foam body. The pusher may be assembled in anymanner so that said pusher is movable toward the bottom plate of thereceptacle so as to compress and displace the plastics foam and toabsorb the kinetic energy developed.

Although certain specific embodiments of the invention have been shownand described, it is obvious that many modifications thereof arepossible. The invention, therefore, is not intended to be restricted tothe exact showing of the drawings and description thereof, but isconsidered to include reasonable and obvious equivalents.

It will thus be seen that the objects set forth above,

among those apparent from the preceding description, are efficientlyattained and, since certain changes may be made in the aboveconstruction without departing from the spirit and scope of theinvention, it is intended that all matter contained in the abovedescription or shown in the accompanying drawings shall be interpretedas illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended tocover all of the generic and specific features of the invention hereindescribed, and all statements of the scope of the invention which, as amatter of language, might be said to fall therebetween.

What is claimed is:

1. A combination safety belt for vehicles comprising a plurality ofbelts for tightly holding an occupant to be protected to a seat bymutually engaging each of the free ends of at least two belts fixed byeach of the other ends to anchoring portions of a vehicle, said safetybelt being characterized in that one of said belts is provided withshock absorbing device along its longitudinal direction, said shockabsorbing device comprising a rigid plastics foam body, a receptaclewith a bottom plate holding said plastics foam body, and a pusher with atapering pushing face situated to hold said plastics foam body betweensaid bottom plate and said tapering pushing face within said receptacle,a tapering pushing face being one which decreases in transverse area inthe direction in which said face moves during absorption of shock, theprojected pushing area of said tapering pushing face being smaller than70 percent of the cross sectional area of the plastics foam body and theprojection ratio of said tapering pushing face being between 0.25 and1.75, said pusher and receptacle being so connected to said safety beltthat stress on said safety belt moves said pusher toward said bottomplate, thereby compressing and crushing said plastics foam body betweensaid pushing face and the inner side wall of said receptacle anddisplacing said crushed plastics foam body toward said inner side wall,whereby the kinetic energy developed by the movement of the occupantagainst the belt is absorbed by the structural compression and crushingof said plastics foam body when a shock is applied to said vehicle, therestraining force exerted by said safety belts against said occupantbeing essentially constant and within tolerable limit during saidstructural compression.

2. A device in accordance with claim 1, wherein the aforesaid structuralcompression causes cellular destruction.

3. A safety belt according to claim 1, wherein a rigid plastics foambody having density of 0.02 to 0.5 g/cm and a permanent set of above 60percent is used.

4. A- safety belt according to claim 3, wherein said rigid plastics foambody is a rigid polyurethane foam body having density of 0.02 to 0.5g/cm and a permanent set of above 60 percent.

5. A safety belt according to claim 3, wherein said rigid plastics foambody is a rigid polystyrene foam body having density of 0.02 to 0.5 g/cmand a permanent set of above 60 percent.

6. A safety belt according to claim 1, wherein said receptacle is acylindrical body having a bottom plate and said pusher has a round base.

7. A safety belt according to claim 6, wherein said tapering pushingface is conically shaped.

8. A safety belt according to claim 6, wherein said tapering pushingface is spherically shaped.

9. A safety belt according to claim 6, wherein said bottom plate has ahole therethrough and said pusher is fixed to a rod proximate the top ofsaid receptacle,

said rod passing through said hole in said bottom plate.

10. A safety belt according to claim 9, wherein said plastics foam bodyis a cylindrical body with an axial penetrating hole and said connectingrod penetrates said penetrating hole of said plastics foam body.

11. A safety belt according to claim 1, wherein said receptacle is abox-shaped body with a square crosssection and said tapering pushingfaces are pyramidal.

12. A safety belt according to claim 11, wherein said pusher is joinedto a connecting rod at the top of said pyramid-shaped pushing faces saidplastics foam body and said bottom plate have a central holetherethrough, and said connecting rod penetrates said central hole insaid plastics foam body and that of said bottom plate of said box-shapedbody.

13. A safety belt according to claim 1, wherein said receptacle is abox-shaped body with a rectangular cross-sectional area and said pusherhas the same constant thickness as the length of the shorter side ofsaid cross-sectional area.

14. A safety belt according to claim 13, wherein said tapered pushingfaces consist of two inclined plane surfaces.

15. A safety belt according to claim 13, wherein said tapered pushingfaces consist of two concave surfaces.

16. A safety belt according to claim 13, wherein said tapered pushingfaces consist of two convex surfaces.

rod within said box-shaped body.

1. A combination safety belt for vehicles comprising a plurality ofbelts for tightly holding an occupant to be protected to a seat bymutually engaging each of the free ends of at least two belts fixed byeach of the other ends to anchoring portions of a vehicle, said safetybelt being characterized in that one of said belts is provided withshock absorbing device along its longitudinal direction, said shockabsorbing device comprising a rigid plastics foam body, a receptaclewith a bottom plate holding said plastics foam body, and a pusher with atapering pushing face situated to hold said plastics foam body betweensaid bottom plate and said tapering pushing face within said receptacle,a tapering pushing face being one which decreases in transverse area inthe direction in which said face moves during absorption of shock, theprojected pusHing area of said tapering pushing face being smaller than70 percent of the cross sectional area of the plastics foam body and theprojection ratio of said tapering pushing face being between 0.25 and1.75, said pusher and receptacle being so connected to said safety beltthat stress on said safety belt moves said pusher toward said bottomplate, thereby compressing and crushing said plastics foam body betweensaid pushing face and the inner side wall of said receptacle anddisplacing said crushed plastics foam body toward said inner side wall,whereby the kinetic energy developed by the movement of the occupantagainst the belt is absorbed by the structural compression and crushingof said plastics foam body when a shock is applied to said vehicle, therestraining force exerted by said safety belts against said occupantbeing essentially constant and within tolerable limit during saidstructural compression.
 2. A device in accordance with claim 1, whereinthe aforesaid structural compression causes cellular destruction.
 3. Asafety belt according to claim 1, wherein a rigid plastics foam bodyhaving density of 0.02 to 0.5 g/cm3 and a permanent set of above 60percent is used.
 4. A safety belt according to claim 3, wherein saidrigid plastics foam body is a rigid polyurethane foam body havingdensity of 0.02 to 0.5 g/cm3 and a permanent set of above 60 percent. 5.A safety belt according to claim 3, wherein said rigid plastics foambody is a rigid polystyrene foam body having density of 0.02 to 0.5g/cm3 and a permanent set of above 60 percent.
 6. A safety beltaccording to claim 1, wherein said receptacle is a cylindrical bodyhaving a bottom plate and said pusher has a round base.
 7. A safety beltaccording to claim 6, wherein said tapering pushing face is conicallyshaped.
 8. A safety belt according to claim 6, wherein said taperingpushing face is spherically shaped.
 9. A safety belt according to claim6, wherein said bottom plate has a hole therethrough and said pusher isfixed to a rod proximate the top of said receptacle, said rod passingthrough said hole in said bottom plate.
 10. A safety belt according toclaim 9, wherein said plastics foam body is a cylindrical body with anaxial penetrating hole and said connecting rod penetrates saidpenetrating hole of said plastics foam body.
 11. A safety belt accordingto claim 1, wherein said receptacle is a box-shaped body with a squarecross-section and said tapering pushing faces are pyramidal.
 12. Asafety belt according to claim 11, wherein said pusher is joined to aconnecting rod at the top of said pyramid-shaped pushing faces saidplastics foam body and said bottom plate have a central holetherethrough, and said connecting rod penetrates said central hole insaid plastics foam body and that of said bottom plate of said box-shapedbody.
 13. A safety belt according to claim 1, wherein said receptacle isa box-shaped body with a rectangular cross-sectional area and saidpusher has the same constant thickness as the length of the shorter sideof said cross-sectional area.
 14. A safety belt according to claim 13,wherein said tapered pushing faces consist of two inclined planesurfaces.
 15. A safety belt according to claim 13, wherein said taperedpushing faces consist of two concave surfaces.
 16. A safety beltaccording to claim 13, wherein said tapered pushing faces consist of twoconvex surfaces.
 17. A safety belt according to claim 13, wherein saidbottom plate has a central hole therethrough and said pusher is providedwith a connecting rod which penetrates said central hole of said bottomplate of said box-shaped body and said box is provided with two plasticsfoam bodies situated on both sides of said connecting rod within saidbox-shaped body.